Clemastine-induced enhancement of hippocampal myelination alleviates memory impairment in mice with chronic pain

Patients with chronic pain often experience memory impairment, but the underlying mechanisms remain elusive. The myelin sheath is crucial for rapid and accurate action potential conduction, playing a pivotal role in the development of cognitive abilities in the central nervous system. The study reveals that myelin degradation occurs in the hippocampus of chronic constriction injury (CCI) mice, which display both chronic pain and memory impairment. Using fiber photometry, we observed diminished task-related neuronal activity in the hippocampus of CCI mice. Interestingly, the repeated administration with clemastine, which promotes myelination, counteracts the CCI-induced myelin loss and reduced neuronal activity. Notably, clemastine specifically ameliorates the impaired memory without affecting chronic pain in CCI mice. Overall, our findings highlight the significant role of myelin abnormalities in CCI-induced memory impairment, suggesting a potential therapeutic approach for treating memory impairments associated with neuropathic pain.

Efficacy and safety of perioperative application of ketamine on postoperative depression: A meta-analysis of randomized controlled studies

Ketamine, a commonly used general anesthetic, can produce rapid and sustained antidepressant effect. However, the efficacy and safety of the perioperative application of ketamine on postoperative depression remains uncertain. We performed a meta-analysis to determine the effect of perioperative intravenous administration of ketamine on postoperative depression. Randomized controlled trials comparing ketamine with placebo in patients were included. Primary outcome was postoperative depression scores. Secondary outcomes included postoperative visual analog scale (VAS) scores for pain and adverse effects associated with ketamine. Fifteen studies with 1697 patients receiving ketamine and 1462 controls were enrolled. Compared with the controls, the ketamine group showed a reduction in postoperative depression scores, by a standardized mean difference (SMD) of -0.97, 95% confidence interval [CI, -1.27, -0.66], P < 0.001, I2 = 72% on postoperative day (POD) 1; SMD-0.65, 95% CI [-1.12, -0.17], P < 0.001, I2 = 94% on POD 3; SMD-0.30, 95% CI [-0.45, -0.14], P < 0.001, I2 = 0% on POD 7; and SMD-0.25, 95% CI [-0.38, -0.11], P < 0.001, I2 = 59% over the long term. Ketamine reduced VAS pain scores on POD 1 (SMD-0.93, 95% CI [-1.58, -0.29], P = 0.005, I2 = 97%), but no significant difference was found between the two groups on PODs 3 and 7 or over the long term. However, ketamine administration distinctly increased the risk of adverse effects, including nausea and vomiting (risk ratio [RR] 1.40, 95% CI [1.12, 1.75], P = 0.003, I2 = 30%), headache (RR 2.47, 95% CI [1.41, 4.32], P = 0.002, I2 = 19%), hallucination (RR 15.35, 95% CI [6.24, 37.34], P < 0.001, I2 = 89%), and dizziness (RR 3.48, 95% CI [2.68, 4.50], P < 0.001, I2 = 89%) compared with the controls. In conclusion, perioperative application of ketamine reduces postoperative depression and pain scores with increased risk of adverse effects.

Contribution of activating lateral hypothalamus-lateral habenula circuit to nerve trauma-induced neuropathic pain in mice

Neuropathic pain, a severe clinical symptom, significantly affects the quality of life in the patients. The molecular mechanisms underlying neuropathic pain have been the focus of research in recent decades; however, the neuronal circuit-mediated mechanisms associated with this disorder remain poorly understood. Here, we report that a projection from the lateral hypothalamus (LH) glutamatergic neurons to the lateral habenula (LHb), an excitatory LH-LHb neuronal circuit, participates in nerve injury-induced nociceptive hypersensitivity. LH glutamatergic neurons are activated and display enhanced responses to normally non-noxious stimuli following chronic constriction injury. Chemogenetic inhibition of LH glutamatergic neurons or excitatory LH-LHb circuit blocked CCI-induced nociceptive hypersensitivity. Activation of the LH-LHb circuit led to augmented responses to mechanical and thermal stimuli in mice without nerve injury. These findings suggest that LH neurons and their triggered LH-LHb circuit participate in central mechanisms underlying neuropathic pain and may be the targets for the treatment of this disorder.

Integrated Proteomic and Phosphoproteomic Analysis of the Hippocampus in a Mouse Model of Early Life Inflammation

INTRODUCTION

Inflammation in early life is a risk factor for the development of neuropsychiatric diseases later in adolescence and adulthood, yet the underlying mechanism remains elusive. In the present study, we performed an integrated proteomic and phosphoproteomic analysis of the hippocampus to identify potential molecular mechanisms of early life inflammation-induced cognitive impairment.

METHODS

Both female and male mice received a single intraperitoneal injection of 100 μg/kg lipopolysaccharide (LPS) on postnatal day 10 (P10). Behavioral tests, including open field, elevated plus-maze, and Y-maze tests, were performed on P39, P40, and P41, respectively. After behavioral tests, male mice were sacrificed. The whole brain tissues and the hippocampi were harvested on P42 for proteomic, phosphoproteomic, Western blot, and Golgi staining.

RESULTS

Early life LPS exposure induced cognitive impairment in male mice but not in female mice, as assessed by the Y-maze test. Therefore, following biochemical tests were conducted on male mice. By proteomic analysis, 13 proteins in LPS group exhibited differential expression. Among these, 9 proteins were upregulated and 4 proteins were downregulated. For phosphoproteomic analysis, a total of 518 phosphopeptides were identified, of which 316 phosphopeptides were upregulated and 202 phosphopeptides were downregulated in the LPS group compared with the control group. Furthermore, KEGG analysis indicated that early life LPS exposure affected the glutamatergic synapse and neuroactive ligand-receptor interaction, which were associated with synaptic function and energy metabolism. Increased level of brain protein i3 (Bri3), decreased levels of PSD-95 and mGLUR5, and dendritic spine loss after early life LPS exposure further confirmed the findings of proteomic and phosphoproteomic analysis.

CONCLUSIONS

Our findings demonstrated that neuroinflammation and impaired synapse may be involved in early life inflammation-induced cognitive impairment. Future studies are required to confirm our preliminary results.

Downregulation of Fat Mass and Obesity-Related Protein in the Anterior Cingulate Cortex Participates in Anxiety- and Depression-Like Behaviors Induced by Neuropathic Pain

N6-methyladenosine (m⁶A) is the most abundant methylation modification on mRNA in mammals. Fat mass and obesity-related protein (FTO) is the main RNA m⁶A demethylase. FTO is involved in the occurrence and maintenance of neuropathic pain (NP). NP often induces mental disorders. We found that NP downregulated the expression of FTO in the anterior cingulate cortex (ACC), inhibited the expression of matrix metalloproteinase-9 (MMP-9) in the ACC, maladjusted the brain-derived neurotrophic factor precursor (proBDNF) and mature brain-derived neurotrophic factor (mBDNF) levels in the ACC, and induced anxiety- and depression-like behaviors in mice. Blocking the downregulation of FTO in the ACC induced by peripheral nerve injury could reverse the anxiety- and depression-like behaviors of mice. Contrarily, downregulation of simulated FTO induced anxiety- and depression-like behaviors in mice. After peripheral nerve injury, the binding of FTO to MMP-9 mRNA decreased and the enrichment of m⁶A on MMP-9 mRNA increased. In conclusion, downregulation of FTO in ACC by regulating MMP-9 mRNA methylation level contributes to the occurrence of anxiety- and depression-like behaviors in NP mice.

Quadratus Lumborum Block Spares Postoperative Opioid Usage but Does Not appear to Prevent the Development of Chronic Pain After Gastrointestinal Surgery

BACKGROUND

Regional anesthesia has been used to reduce acute postsurgical pain and to  prevent chronic pain. The best technique, however, remains controversial.

OBJECTIVES

The aim of this study was to assess the short- and long-term postoperative analgesic efficacy of ultrasound-guided quadratus lumborum block (QLB) in open gastrointestinal surgery.

STUDY DESIGN

A randomized, double-blinded, controlled trial.

SETTING

Operating room; postoperative recovery room and ward.

METHODS

One hundred eighteen patients underwent elective gastrointestinal surgery randomly assigned into 2 groups (QLB group or control group). Before anesthetic induction, QLB was performed bilaterally under ultrasound guidance using 20 mL of 0.375% ropivacaine or saline solution at each abdominal wall. The primary outcome was cumulative oxycodone consumption within 24 h after surgery. The secondary outcomes were acute pain intensity, incidence of chronic pain, and incidence of postoperative nausea or vomiting (PONV), dizziness, and pruritus.

RESULTS

The cumulative oxycodone consumption was significantly lower in the QLB group during the first 6, 6-24, 24, and 48 h postoperatively when compared to the control group. At rest or during coughing, the numeric rating scale scores were significantly lower at 1, 3, 6, and 12 h postoperatively in the QLB group compared to the control group. There were no significant differences between the 2 groups regarding the incidence of chronic postoperative pain at 3 or 6 months after surgery. Significant differences were found in the incidence of PONV between the two groups, but other complications, such as dizziness and pruritus, did not differ significantly.

LIMITATIONS

We did not confirm the QLB effectiveness with sensory level testing after local anesthetic injection. Cumulative oxycodone consumption could have been affected by the patients' use of oxycodone for nonsurgical pain.

CONCLUSIONS

Ultrasound-guided QLB provided superior short-term analgesia and reduced oxycodone consumption and the incidence of PONV after gastrointestinal surgery. However, the incidence of chronic pain was not significantly affected by this anesthetic technique.

Selection of immunodominant mimics of IROMP-99 of rabbit Pasteurella multocida from a random 12-peptide library

A random 12-peptide library was used to screen immunodominant mimics of 99kDa iron-regulated outer membrane protein (IROMP-99) of rabbit Pasteurella multocida. In the present study, expression of IROMPs of rabbit P. multocida strain C51-12 were analyzed by SDS-PAGE, and Western blot to determine the specificity of rat antiserum antibodies against IROMP-99. Only IROMP-99 whose expression was induced under iron-restricted conditions was detected on nitrocellulose paper. The phage display library was screened with rat normal and IROMP-99-specific antiserum. The positive phage clones were identified using enzyme-linked immunoadsorbent assay (ELISA) and inhibition assays for their reactivity to the antiserum. Out of the 18 randomly selected positive clones that showed higher reactivity to rat antiserum, only ten clones efficaciously inhibited binding of rat antisera to IROMPs and their displayed peptides were determined. Alignment using DNAStar-MegAlign software, results showed that motif WHxTxP was highly conserved among nine clones, only clone A7 had no obvious linear homology with either. Our findings suggest that the motif WHxTxP could be an immunodominant mimic epitope of IROMP-99 of rabbit P. multocida strain C51-12.